The present invention relates to an apparatus for producing a wound coil from an elastic material, for example a plastic material such as polyester or polyamide. More specifically, the present invention relates to such an apparatus for producing continuously a wound coil of such a material, for example from thermoplastic monofilaments, whereby the material stabilizes upon the application of heat.
There is known, for example from DE-AS 11 52 529, an apparatus of this general type wherein a feed mechanism supplies thermoplastic monofilaments through a coiling head over a winding cone to a winding mandrel which has a length to extend at least through a stabilizing conduit or zone, through which the wound coil is fed while being heated, thereby stabilizing the coil. In this known apparatus, the wound coil is fed by two screw conveyors provided in the stabilizing conduit, thereby resulting in parting of the coil, which is undesirable for certain applications. The capacity of this known apparatus is limited by the screw conveyor transmission system, since the contact surface of the wound coil at the screw conveyor melts due to additional friction heat.
In other known devices, a wound coil is passed through a stationary conduit or zone and is heated therein for stabilization, for example by infrared radiation. In this type of apparatus, polyester which need only be heated slightly in order to be stabilized can be handled with relative ease. For polyamides however, which must be heated to approximately 150.degree. to 260.degree. C. to be stabilized, this known system results in considerable problems.
Thus, to bring an endlessly moving polyamide monofilament to a temperature of 150.degree. to 260.degree. C. by means of radiant heat, a relatively long exposure time is necessary. This could be achieved by an appropriately long stabilization conduit, except for the fact that polyamides have a tendency to become unstable at relatively high temperatures, the result of which is that the winding of the coil on the mandrel no longer moves the previously wound coil ahead. Therefore, the coil as a whole no longer will be moved forward through the stabilizing conduit or zone. However, in such a long stabilizing conduit, if additional mechanical devices are provided to move the wound coil forward along the winding mandrel, such devices will cause the coil to be deformed if it is soft. Accordingly, it is extremely difficult to form polyamide filaments into wound coils, for example such as are required for link belts.